1. Technology Field
The present invention generally relates to intravascular stent systems. In particular, the present invention relates to a stent delivery catheter system that facilitates the accurate positioning of a stent with respect to an ostium of a bifurcated body vessel.
2. The Related Technology
Angioplasty and stent implantation procedures are commonly employed to treat lesions or blockages that form within the vascular anatomy of a patient. During an angioplasty, or percutaneous transluminal coronary angioplasty (“PTCA”) procedure, for instance, a guiding catheter is advanced through the vasculature of the patient to a desired point, such as the ostium of a predetermined coronary artery. A guidewire, positioned within a balloon catheter, is extended from a distal end of the guiding catheter into the patient's coronary artery until it penetrates and crosses a lesion to be dilated. The balloon catheter is then advanced through the guiding catheter and over the previously introduced guidewire, until it is properly positioned across the lesion.
Once properly positioned, the balloon is inflated to a predetermined size such that the stenosis of the lesion is compressed against the arterial wall, thereby expanding the passageway of the artery. The balloon is subsequently deflated, blood flow resumes through the dilated artery, and the balloon catheter is removed.
Occasionally, post-procedure restenosis, or reformation of the arterial blockage, occurs after the PTCA procedure has been performed. Or, a dissection in the blood vessel wall caused by the balloon angioplasty procedure may occur. In addition, elastic recoil and remodeling of the vessel wall after the angioplasty procedure can result. To correct these side effects and strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. During a stent implantation procedure, a stent is delivered in a contracted state on a balloon catheter to the desired location within a coronary artery.
Once properly positioned, the stent is expanded to a larger diameter via expansion of the balloon, which causes the stent to expand against the arterial wall at the lesion site. The balloon is then deflated and it and the catheter are withdrawn. The expanded stent remains in place within the artery at the site of the dilated lesion, holding the vessel open and improving the flow of blood therethrough. Stents have been successfully implanted in the z urinary tract, the bile duct, the esophagus and the tracheo-bronchial tree to reinforce those body organs, as well as implanted into the neurovascular, peripheral vascular, coronary, cardiac, and renal systems, among others.
Lesions are often located at or near a point of bifurcation in an artery or other body vessel. When treating such bifurcated lesions, it is common to first place a first guidewire in the main branch, then place a second guidewire, extending from the main branch, into the side branch of the vessel bifurcation. This is so because it is generally important to preserve the side branch and the main branch of the bifurcation.
Specifically, in some instances the above-described dilation via PTCA procedure causes plaque to be shifted from the treated main branch of the vessel bifurcation to the non-treated vessel side branch, thereby occluding the side branch. This effect is known as the “snowplow” effect. Prior placement of the second guidewire in the vessel side branch enables treatment of the side branch should it become occluded due to the snowplow effect.
Treatment of the side branch in this case often includes deployment of a stent therein. The stent is desirably placed in the vessel side branch and deployed so that its proximal end is disposed as close to the ostium, or side branch vessel opening, as possible.
Particularly, it is desired for a stent in a side branch to be positioned axially so as to cover the entirety of the side branch ostium. However, care must also be taken so as to avoid placing the stent such that it “overhangs” beyond the side branch ostium into the lumen of the main branch proximate the ostium. If such overhanging occurs, proper placement of a stent subsequently in the main branch could be compromised undesirably causing, among other things, inhibited blood flow through the stented region. At the same time, placing the stent too far distally into the side branch lumen prevents the stent from adequately covering the ostium, which can make the ostium region susceptible to further degradation or formation of stenoses.
As seen by the above discussion, therefore, it is sometimes necessary in the treatment of lesions at a bifurcated vessel site to deploy a stent in the side branch of the bifurcation. It is paramount, however, to accurately place the stent axially within the side branch so as to avoid the problems described above.
Yet another challenge relating to the placement of a stent relates to the difficulty encountered in maneuvering the stent during its intraluminal transit to the stent deployment site. Particularly, advancement of the stent via the typically tortuous vessel path is made more difficult by the inability to adequately control the rotation of the stent deployment assembly relative to the main branch and side branch of the bifurcated vessel.
In greater detail, during advancement of a catheter along a predisposed guidewire as described earlier, the bifurcation stent deployment assembly, which is coupled with the catheter to support and transport the bifurcation stent in a collapsed state, is not rotatably controlled. Hence, it is often necessary to rotate and reorient a distal portion of the catheter about its longitudinal axis in order to ensure proper alignment of the stent relative to the side branch before its deployment therein.
Unfortunately, transmitting a controlled rotation to the distal end of the catheter over the length of the flexible catheter shaft, however, had traditionally proven difficult. This difficulty is due in part to the complex anatomy of a coronary artery, which results in the flexible catheter shaft being unable to adequately transfer an imposed rotational torque to a distal portion of the catheter shaft where the stent deployment assembly is positioned. Instead, the elongated, flexible catheter shaft merely rotates at the proximal portion when twisted without transmitting the rotational torque distally to the stent deployment assembly in a consistent or satisfactory manner.
Accordingly, there is a need for a stent delivery system with improved alignment and orientation capabilities for aligning a distally positioned stent for deployment within the lumen of a body vessel. More particularly, a need exists for a stent delivery system capable of enabling precise axial and radial positioning of the stent for placement at a vessel bifurcation, for instance, so as to enable the ostium of such a bifurcation to be adequately covered by the stent while preventing undesirable overhang of the stent into proximate areas of the bifurcation.